1. Field of the Invention
The present invention relates to footwear. In particular, the present invention is related to strapping systems for securely affixing footwear to a user""s foot, and to shanks for providing rigidity and support to shoe soles.
2. Background of the Invention
There is a wide variety of prior art showing strapping configurations for footwear. Generally, the purpose of such strapping may be summarized as securing the footwear to a user""s foot and is often used in connection with sandals.
Examples of prior art showing sandal or footwear strapping arrangements include U.S. Pat. Nos. 4,200,997 and 4,446,633 to Scheinhaus, U.S. Pat. No. 4,679,334 to McBride, U.S. Pat. No. 3,327,410 to Park, U.S. Pat. No. 4,793,075 to Thatcher, U.S. Pat. No. 4,817,302 to Saltsman, U.S. Pat. No. 4,300,294 Riecken, U.S. Pat. No. 2,788,591 to Gibson, U.S. Pat. No. 2,126,094 to Daniels, and U.S. Pat. No. 2,862,311 to Ellis. Each of these patents disclose strapping configurations which generally engage the ankle, heel, instep, toes, arch, or some combination thereof to secure the footwear to the user""s foot. None of these prior art disclosures, however, nor any other existing strapping configurations have been entirely satisfactory in securing footwear to the foot while maintaining a comfortable, durable, and convenient configuration. This problem is particularly acute for sandals used in sports or other vigorous activities. As sandals have become more frequently worn in these active endeavors, demands on strapping configurations have grown. No known existing sandal strapping configuration allows for the natural adjustments of the foot and ankle during activity; such adjustments would enhance user comfort and ease of use.
One particular problem relates to ankle or instep straps. As the angle between the foot and the ankle changes during normal walking or running, the foot""s main tendon that travels down the front of the leg and across the instep of the foot is alternately tightened and loosened. This causes the overall circumference of the ankle and instep to increase and decrease. Any strapping that wraps the ankle must allow for this expansion and contraction, which necessitates such strapping to be able to compensate for the size variation. Without such compensation, the ankle strapping may overly restrict foot movement.
Prior footwear straps are typically oriented in a direction that does not correspond to the force vectors that occur during walking, running, or vigorous activity. Strapping usually is oriented at an angle of approximately 90xc2x0 from the sole. This angle is appropriate to maximize strapping strength only when the strap lies flat and parallel to the sole on the foot surface. As the top of the foot slopes forward, however, a strap oriented at a 90xc2x0 angle from the sole must twist to lie flat on the sloping foot surface. This causes discomfort in the user and diminishes the strength capacity of the strap.
Still other prior art footwear strapping configurations feature a continuous strap that contacts the wearer""s foot in multiple locations, such as around the ankle, across the instep, and over the front of the foot. Such straps cannot remain taut during activity, due to movement of other portions of the foot. A continuous strap that covers both the instep and the forefoot, for instance, may lack the continuous, taut fit over the instep due to movement of the forefoot.
In addition to footwear strapping systems, other problems related to movement of the sole in relation to the foot also remain unresolved by the prior art. In particular, difficulties are associated with providing torsional rigidity, arch support, and overall stiffness to a sole during walking, running, or other vigorous activity. While a generally soft and cushioned sole forefoot and heel portion are desirable for wearer comfort, they may result in a sole being undesirably soft and xe2x80x9cfloppyxe2x80x9d. To prevent this condition, a relatively stiff and rigid shank may be provided to bridge the softer, less rigid forefoot and heel portions. The more rigid shank also provides torsional rigidity to the sole, preventing undesirable twisting motions during a wearer""s stride.
Prior art shanks include metal plates inserted in the midfoot region between the midsole and either an outsole or an insole; a laterally narrow section of rubber or other material attached to the bottom outsole in the midfoot region (generally known as a xe2x80x9cfiddleshankxe2x80x9d); and other plastic components molded or glued to the sole midfoot region for support and rigidity. Such prior art shanks do not, however, adequately prevent and generally, are not well-configured to counteract the twisting type of torsional forces developed during wearing of footwear, especially those forces caused by straps that pass through the sole.
Numerous unresolved needs therefore exist relating to footwear. A long felt need exists for a footwear strapping configuration that accommodates the foot""s wide range of movement during sports or other vigorous activities. In addition, a need exists for strapping that is capable of dynamically adjusting itself as required during such use. Further, unresolved needs exist for an integral, stiff and rigid shank portion to provide torsional rigidity and stiffness to an otherwise relatively soft and cushioned footwear forefoot and heel portions.
A first embodiment of the present invention comprises a unique strapping configuration for footwear that provides for dynamic fit adjustment while securely and comfortably affixing a sole to a wearer""s foot. The strapping generally includes an adjustable X configuration strap which is attached in some manner to a heel portion of the footwear, crosses over the wearer""s instep, and passes through a transverse channel in the midsole of the footwear under the wearer""s arch. The present invention further comprises footwear incorporating the unique strapping configuration that securely fastens the footwear to the user""s foot, even during sports or other vigorous activities.
The adjustable X configuration instep strap generally has a first end secured to a first side of a heel portion of the footwear, crosses forwardly and transversely over the wearer""s instep, passes through a channel in the sole of the footwear at the midfoot, the longitudinal center of the sole, extends rearwardly and transversely back across the wearer""s instep (thereby forming an X over the instep), and is adjustably and releasably secured to the second side of the heel portion of the footwear. The channel may be angled downwardly from rear to front in the longitudinal direction, parallel to the downward slope of the wearer""s instep, so that the strap will lie flat on the wearer""s instep and thereby more evenly carry forces that develop between the foot and the sole during sports or other vigorous activities.
The X configuration instep strap acts to secure the wearer""s foot to the footwear sole. The strap preferably passes under the wearer""s arch through the midfoot channel, and thereby works to secure the transverse midfoot portion of the sole to the bottom of the wearer""s foot.
The portion of the footwear sole through which the midfoot channel passes, the midfoot shank, is preferably comprised of a relatively stiff and hard material. Incorporation of such shank material enables the channel to not significantly compress and thereby not pinch the strap passing through it during use. The strap may thus be free to move through this channel as the foot moves in different directions during use. The sole including the arch channel may be manufactured separate from the sole and may be affixed thereto by molding or with an adhesive. This allows for the shank including the midfoot channel to be constructed of a relatively hard and stiff material and to be conveniently attached to a softer, more pliable sole. Alternatively, the shank portion may also be an integral portion of the sole. The relatively stiff and resilient arch channel also functions as a standard type shank to add desirable stiffness and torsional rigidity to the sole, as will be discussed in greater detail below in relation to additional embodiments of the invention.
In addition to the X-strap of the invention, the preferred sandal embodiment further may comprise a front strap system for releasably attaching the sole to the forefoot, and a heel strap system for releasably attaching the sole to the wearer""s heel. Preferably, the heel strap system may include a pair of opposing heel posts that may extend upward from the sole at the medial and lateral sides of the heel portion of the sole. Further, the heel strap system may include a T-strap having a downwardly extending portion that attaches to the center, rear of the sole, behind the wearer""s Achilles tendon. The two free ends of the X-strap can be connected to the front of the lateral and medial heel posts. A side member or lateral strap may be further used that extends from the lateral heel post to the front strap to provide additional support for the foot. However, additional strap configurations now known or hereafter devised by those skilled in the art may be utilized.
As indicated above, the present invention optionally further comprises a footwear sole having relatively soft, low density forefoot and heel portions with a higher density, more rigid shank portion. The two distinct density materials may be hot compression molded together to from a structurally integral unit. The high density, more rigid shank portion of the invention may, but need not, comprise the transverse channel described above for passing a strap. In addition, the sole of the invention may be particularly well suited for, but is not limited to, use in sandals.
In accordance with various aspects of the present invention, the sole may comprise a molded unit of two or more different densities of thermoplastic or thermosetting polymer compounds. One compound may be of suitably low density and hardness to provide flexibility and cushion. Near the midfoot region of the sole, underlying the user""s arch, is a shank portion comprising a denser, harder, stiffer compound. The presence of the higher density, stiffer shank tends to insure that the arch of the foot will have improved support. In addition, the relatively stiff shank is desirable to lend structure and support to the sole at the midfoot region where the outsole does not touch the ground, to provide a desirable overall stiffness to the sole during walking, and to provide torsional rigidity. The structural effect of the shank may be easily controlled by varying the hardness of the shank as desired.
Before explaining the several embodiments of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.
The advantages of the present invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings.